The present invention relates to a piezoelectric vibrator and a vibrator-type actuator.
A vibrator-type actuator using a piezoelectric vibrator as an electromechanical conversion means for application to a miniaturized and high-torque producing apparatus in a precision mechanical equipment has been developed. Particularly, ultrasonic motors have been developed and put into practical use as vibrator-type actuators.
So far three types of ultrasonic motor systems have been developed. The first is the so-called "travellingwave-type" or "mode rotation-type"; the second is the "standing wave-type", which is based upon the standing wave; and the third is the "multi resonance-type". The typical structures and operational principles of these motor systems are disclosed in papers: "Ultrasonic Motors Using Piezoelectric Multi-Mode Vibrators" by Takehiko Tanaka et al., Japanese Journal of Applied Physics, Vol. 27 (1988) Supplement 27-1, pp. 192-194, and "Construction of Ultrasonic Motors and their Applications" by Yoshiro Tomikawa et al., Japanese Journal of Applied Physics, Vol. 27 (1988) Supplement 27-1, pp. 195-197.
The above known ultrasonic motors are, however, complex in both mechanical and circuit structure with respect to the driving circuit for the piezoelectric vibrator. As a result these structures cause problems and difficulty in miniaturization and cost reduction.
In a prior U.S. application Ser. No. 07/357,733 by the same applicant, there are proposed a new structure and several apparatuses for applications of the vibrator-type actuator.